This section provides background information related to the present disclosure which is not necessarily prior art.
Hybrid vehicles may include an internal combustion engine and a hybrid power assembly. Hybrid vehicles may be operated during extended periods of time in a hybrid mode using only the hybrid power assembly. During operation in the hybrid mode, the engine may be off. When the vehicle is switched to an engine operating mode, exhaust gas exiting the engine passes through an exhaust aftertreatment system. Components of the exhaust aftertreatment system may require minimum operating temperatures for proper operation. The engine may be powered on during the hybrid mode, even when not needed for additional power output, in order to maintain the exhaust aftertreatment system at a desired operating temperature. This results in reduced fuel economy.